Triple section mast with high free lift



Feb. 20, 1968 G. P. MARCO TRIPLE SECTION MAST WITH HIGH FREE LIFT FiledApril 13, 1967 United States Patent 3,369,632 TRIPLE SECTION MAST WITHHIGH FREE LIFT George P. Marco, Homewood, Ill., assignor to Allis-Chalmers Manufacturing Company, Milwaukee, Wis. Filed Apr. 13, 1967,Ser. No. 630,756

Claims. (Cl. 187-9) ABSTRACT OF THE DISCLOSURE The drawings illustrate ahigh free lift triple section mast for a lift truck having low collapsedheight and relatively high extended height. Two of the three componentsof the lift jack are connected to two of the three sections of the mastand the third component of the lift jack carries a pulley engaging aflexible lift element secured at one of its ends to the carriage and atits other end to the stationary mast section. The flexible lift elementis also reeved about pulleys at opposite ends of mast section on whichthe load carriageis mounted.

This invention relates to a triple section mast wherein the loadcarriage may be raised to the collapsed height of the mast before themast height is increased. In other words this invention relates to ahigh free lift, triple section mast. h

A high free lift mast is particularly useful in loading and unloadingbox cars or semitrailer trucks. In such operations it is also desirablethat the collapsed height of the mast be fairly low so that the lifttruck may be moved through low doorways, such as those encountered inbox cars, trucks and some warehouses. While a low collapsed height ofthe mast is desired, the warehouse to or from which the cargo is beingmoved may have a sufiiciently high ceiling to permit stacking of storedmaterial to a fairly high height. Thus it is often desired that the mastwith low collapsed height also have a relatively great extended height.It is a primary objective of the present invention to provide a mastwhich fulfills the hereinbefore outlined requirements in an entirelysatisfactory manner.

It is a further object of this invention to provide a mast of thehereinbefore character which is economical to manufacture and isentirely satisfactory in operation.

It is a further object of this invention to provide a high free liftmast assembly with at least three sections wherein the lift jack andchain and sprocket arrangement insure the proper sequence of movement ofthe mast sections without requiring use of latches.

These and other objects and advantages of this invention will beapparent to those familiar with the art when the following descriptionis read in conjunction with the drawings in which:

FIG. 1 is a vertical section view of a triple section mast incorporatingthe present invention;

FIG. 2 is a view of the mast shown in FIG. 1 with the carriage raised tothe top of the mast to illustrate the full free lift available;

FIG. 3 is a view of the mast shown in FIGS. 1 and 2 with the mastextended to an intermediate position;

FIG. 4 is another view of the mast shown in FIGS. 1, 2 and 3, butextended to its full height;

FIG. 5 is an enlarged top view of the mast taken along the line VV inFIG. 1; and

FIG. 6 is an enlarged section View taken along the line VIVI in FIG. 3.

As shown in the drawings, the mast assembly includes a stationary outeror primary section 11 pivotally mounted on a lift truck chassis 8 bypins 9, 9'. The primary mast section has a pair ofbrackets 10, 10'adapted for connection to tilt jacks, the brackets being welded toupright guide or channel members 12, 13 which are tied together by crossbraces 14, 15 and a bottom plate 16. A pair of rollers 17, 18 arerotatably secured to the channel members 12, 13 and extend throughcutout portions 19, 21 to engage upright guide members or I-beams 22, 23forming part of a second or intermediate mast section 24. The I-beams22, 23 are tied together by cross braces 26, 27 and carry a pair ofrollers 28, 29 which extend through notches 33, 34 and abut I-beams 31,32 of an inner or third mast section 30. The inner mast section 30 isreinforced by a cross member 36 secured to the top of guides 31, 32 andby a cross member 37 secured to the lower rear of the I-beams or guidemembers 31, 32. A lift fork carriage 41 with forks 40 is mounted forvertical reciprocal movement in the guide members 31, 32 by rollers 42,43. A lift mechanism, 7 including a hydraulic jack 46 and flexible liftelements in the form of a pair of continuous sprocket chains 47, 47, isemployed for operating the mast. The chains 47, 47' are anchored at oneend to the carriage, as at point 48, and to the bottom of the outer mastsection 11 as at point 49. Between the carriage and primary mast sectionthe chains 47, 47 are reeved over a pair of pulleys in the form ofsprockets 51, 51 thence over a pair of pulleys in the form of sprockets52, 52' pivotally mounted to the bottom of the inner mast section 30,thence over a pair of pulleys in the form of sprockets 53, 53' mountedon the upper end of component 54 of jack 46. The jack 46 is acommercially available high free lift cylinder assembly. As shown inFIG. 1, the extensible cylinder component 54 of jack 46 is in itsretracted position and the carriage 41 is in its lowermost position.When the jack 46 is initially supplied pressure fluid from pump 71through control valve 72 and conduit 73, the cylinder component 54 willtelescopically displace itself upwardly relative to the outercylindrical component 56. The component 56 includes an integrally formedinner cylindrical portion 57 which extends the entire collapsed heightof jack 46. The cylinder component 54 is in the nature of a sleeve whichmounts a crosshead 58 carrying sprockets 53, 53. The upper end ofcylinder part 57 is secured to a bracket 59 at the upper end of theintermediate mast section 24.

As will be noted in FIG. 2, the carriage 41 has been raised to the topof the mast in its collapsed condition. Thus the mast provides full freelift. Free lift refers to the distance which the carriage can be raisedfrom the floor before the mast is extended in height. Thus it will beapparent that normal cargo carried by the forks 40 on the carriage maybe raised to the uppermost position required within a box car or truckwithout danger of the mast being pushed through the roof. Upon apredetermined quantity of pressure fluid being supplied to jack 46, thecarriage will move to its one hundred percent free position illustratedin FIG. 2 and when additional pressure fluid is supplied to the jack 46,the cylinder component 56 will be moved upwardly relative to stationarycomponent or inner cylinder 61 which has its bottom end secured to thecross plate 16 at the bottom of the outer mast section 11. This willcause the intermediate mast section 24 to move upwardly relative to theouter mast section 11 and will simultaneously cause the inner mastsection and carriage 41 to move upwardly relative to intermediate mastsection 24.

As shown in FIG. 3 the mast has been extended to an intermediateposition and as shown in FIG. 4 the jack 46 has been completely extendedwhich has caused the mast to be extended to its highest position.

From the foregoing description it will be apparent that I have providedan extremely useful and novel triple section high free lift mastassembly affording low collapsed height for low doorways of box cars andtrucks and relatively high extended height for stacking cargo in highceiling warehouses.

The embodiments of the invention for which an exclusive property orprivilege is claimed are defined as follows:

1. In a multiple section mast assembly for a lift truck,

an upright primary mast section for stationary mounting on a lift truck,

a second mast section mounted for relative vertical reciprocal movementon said primary mast section,

a third mast section mounted for relative vertical reciprocal movementon said second mast section,

a carriage mounted for relative vertical reciprocal movement on saidthird mast section,

a hydraulic jack mounted upright on said mast and having first, secondand third relatively reciprocable components, the first component beingsecured to the bottom end of said primary mast section and the secondcomponent being secured to said second mast section,

a first pulley on the upper end of said third mast sec tion,

a second pulley on the bottom end of said third mast section,

a third pulley on said third component of said jack, and

a flexible lift element having opposite ends secured to said carriageand primary mast section, respectively, and reeved sequentially fromsaid carriage to said primary mast section over said first, second andthird pulleys,

initial predetermined supply of pressure fluid to said jack causing saidthird component to move said carriage to the upper end of said thirdmast section without moving said mast sections upwardly and furthersupply of pressure fluid to said jack extending the latter causing saidcarriage and third mast section to move upwardly relative to said secondmast section and simultaneously causing the latter to move upwardlyrelative to said primary mast section.

2. The structure set forth in claim 1 wherein said third component ofsaid jack moves upwardly upon said jack being initially supplied withpressure fluid and wherein said third pulley is on the upper end of saidthird component of said jack.

3. The structure set forth in claim 1 wherein the upper end of saidsecond jack component is secured to the upper end of said second mastsection.

4. The structure set forth in claim 3 wherein said third pulley is onthe upper end of said third component of said jack.

5. The structure set forth in claim 4 wherein said flexible element issecured at one of its ends to the lower end of said primary mastsection.

References Cited UNITED STATES PATENTS 2,670,811 3/1954 Shaffer 187-92,973,835 3/1961 Quayle 187-9 3,187,842 6/1965 Quayle 187-9 ANDRES H.NIELSEN, Primary Examiner.

H. C. HORNSBY, Assistant Examiner.

